# Hybrid-Electric Vehicle with Natural Gas-Diesel Engine

^{*}

## Abstract

**:**

## 1. Introduction

#### 1.1. Carbon Dioxide Emissions of a Vehicle

#### 1.2. Required Fuel Energy of a Vehicle

#### 1.3. Influence of Hybridization

#### 1.4. Dual-Fuel Natural Gas-Diesel Engine

#### 1.5. Contribution

#### 1.6. Outline

- In Section 2, the materials and methods used are described, including details on the engine test bench, information on engine control, a description of the measurement devices installed and of calculations based on the measurement results as well as details on hardware-in-the-loop experiments and a description of the component models used.
- Section 3 contains the results, including those of static engine measurements of the natural gas-Diesel engine and of the vehicle emulation results.
- In Section 4, a summary is given and conclusions are drawn.

## 2. Materials and Methods

#### 2.1. Engine Test Bench

- port-fuel injection system for gaseous fuels;
- low-pressure exhaust gas recirculation system; and
- cylinder-pressure sensors in all four cylinders.

Engine Type | Volkswagen TDI 2.0-475 NE (CJDA), industrial engine |

Cylinders | 4 |

Displ. Volume | 1.968 L |

Bore | 81.0 mm |

Stroke | 95.5 mm |

Compression Ratio | 16.5 |

Injection System | Bosch common rail with piezo injectors |

#### 2.2. Engine Control

#### 2.3. Measurements and Calculations

#### 2.3.1. Measurements

- Engine torque is measured with an in-line torque transducer “Vibrometer TG20BP” with a nominal torque of 200 $\mathrm{N}\mathrm{m}$ and a maximum measurement torque of 400 $\mathrm{N}\mathrm{m}$;
- Engine speed is measured with an incremental angular encoder “Haidenhein ROD 426” with 1800 pulses. The encoder is connected to the crankshaft of the engine;
- Diesel consumption is measured with a scale “Mettler Toledo MS 6002S/01” with a resolution of $0.01\phantom{\rule{0.166667em}{0ex}}g$. The Diesel consumption is the difference of the weight of the Diesel tank between the start and the end of the measurement;
- Gas consumption is measured with a coriolis mass flow meter “Rheonik RHM015”. Its signal conditioning unit generates a pulse every $0.1\phantom{\rule{0.166667em}{0ex}}g$. Total gas consumption is obtained by summing up these pulses. Total gas consumption is additionally measured with another scale “Mettler Toledo MS 32001L/01” with a resolution of $0.1\phantom{\rule{0.166667em}{0ex}}g$. The consumption is the difference of the weight of the gas bottle between the start and the end of the measurement;
- Nitrogen oxide emissions are measured with a “Continental Smart NO${}_{x}$ Sensor”, and with a “Cambustion fNOx 400”;
- Air-fuel ratio is also measured with the same “Continental Smart NO${}_{x}$ Sensor”;
- Soot is measured with an “AVL Micro Soot Sensor”.

#### 2.3.2. Calculations

- Engine Efficiency is calculated based on the following Equation:$${\eta}_{\mathrm{ICE}}=\frac{{\int}_{\mathrm{Injection}\mathrm{On}}\left({T}_{ICE}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{\omega}_{ICE}\right)\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}dt}{{m}_{D}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}H{l}_{D}+{m}_{G}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}H{l}_{G}}$$
**Table 2.**Fuel Properties.Parameter Diesel Methane Natural Gas Lower heating value (MJ/kg) 43.1 50.02 46.11 Mass $C{O}_{2}$ emitted per mass of fuel burnt (-) 3.16 2.74 2.61 - Gas Ratio is the energetic gas ratio with respect to the total fuel energy. The ratio is calculated based on the following Equation:$${r}_{\mathrm{G}}=\frac{{m}_{G}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}H{l}_{G}}{{m}_{G}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}H{l}_{G}+{m}_{D}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}H{l}_{D}}$$
- Nitrogen oxide emissions are measured in parts per million. To convert that value to gram per kilowatt hour, the following assumptions are made:
- -
- NO${}_{x}$ only consists of NO;
- -
- Diesel is represented by ${C}_{8}{H}_{18}$; and
- -
- Air consists of 21% ${O}_{2}$ and 79% ${N}_{2}$.

$$({n}_{G}+8{n}_{D})\phantom{\rule{4pt}{0ex}}C{O}_{2}+(2{n}_{G}+9{n}_{D})\phantom{\rule{4pt}{0ex}}{H}_{2}O+(2{n}_{G}+12.5{n}_{D})\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\left(\lambda \phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}3.76\phantom{\rule{4pt}{0ex}}{N}_{2}+(\lambda -1)\phantom{\rule{4pt}{0ex}}{O}_{2}\right)$$$$N{O}_{x}[g/kWh]=\phantom{\rule{4pt}{0ex}}\frac{\frac{{m}_{G}}{{M}_{C{H}_{4}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\left(9.5\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\lambda +1\right)+\frac{{m}_{D}}{{M}_{{C}_{8}{H}_{18}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\left(59.5\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\lambda +4.5\right)}{\int {T}_{ICE}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{\omega}_{ICE}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}dt\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\frac{1}{3600\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{10}^{3}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{M}_{NO}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\frac{N{O}_{x}\left[ppm\right]}{{10}^{6}}$$ - Soot is measured in milligram per cubic meter with respect to standard temperature and pressure. The conversion to milligram per kilowatt hour is similar to the conversion of the nitrogen oxide emissions:$$Soot\phantom{\rule{4pt}{0ex}}[mg/kWh]=\phantom{\rule{4pt}{0ex}}\frac{\frac{{m}_{G}}{{M}_{C{H}_{4}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\left(9.5\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\lambda +1\right)+\frac{{m}_{D}}{{M}_{{C}_{8}{H}_{18}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\left(59.5\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\lambda +4.5\right)}{\int {T}_{ICE}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{\omega}_{ICE}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}dt\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\frac{1}{3600\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{10}^{3}}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}\frac{R\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{T}_{STP}}{{p}_{STP}}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}Soot\phantom{\rule{4pt}{0ex}}[mg/{m}^{3}]$$
- Carbon dioxide emissions are calculated based on the measured fuel consumption:$${m}_{{\text{CO}}_{2}}={\nu}_{D}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{m}_{D}+{\nu}_{G}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{m}_{G}$$

#### 2.4. Vehicle Emulation (Hardware-in-the-Loop Experiments)

#### 2.4.1. Powertrains Investigated

**Figure 3.**Powertrains investigated: Conventional (non-hybrid) vehicle on the left-hand side. Hybrid-electric vehicle on the right-hand side.

#### 2.4.2. Longitudinal Vehicle Dynamics

#### 2.4.3. Gearbox

Gear | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
---|---|---|---|---|---|---|---|

$ig$ | 15.943 | 10.038 | 6.359 | 4.335 | 3.205 | 2.501 | 1.995 |

η | 0.97 | ||||||

${T}_{0}$ | ${T}_{nom}\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}6\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{10}^{-3}$ |

#### 2.4.4. Generator

#### 2.4.5. Electric Motor

#### 2.4.6. Battery

Parameter | Value | Unit | Parameter | Value | Unit |
---|---|---|---|---|---|

${V}_{\text{oc},\text{cell}}$ | 3.3 | $\mathrm{V}$ | ${P}_{\text{max},\text{cell}}$ | 400 | $\mathrm{W}$ |

${Q}_{\mathrm{cell}}$ | 4.5 | $\mathrm{A}\mathrm{h}$ | η | 0.98 | - |

${R}_{\mathrm{cell}}$ | 5 | $\mathrm{m}$Ω | ${m}_{cell}$ | 205 | $\mathrm{g}$ |

#### 2.4.7. Vehicle Parameters

Vehicle | Hybrid | Conventional | |||
---|---|---|---|---|---|

Subcompact | Compact | Full-size | Full-size | ||

Mass base vehicle (kg) | 855 | 1313 | 1735 | 1735 | |

Mass hybridization (kg) | 41 | 55 | 69 | - | |

Mass gas (kg) | 12 | 18 | 24 | 24 | |

Mass gas tank (kg) | 35 | 53 | 70 | 70 | |

Total mass vehicle (kg) | ${m}_{\mathrm{v}}$ | 943 | 1439 | 1898 | 1829 |

Aerodynamic drag coefficient (-) | ${c}_{\mathrm{d}}$ | 0.25 | 0.27 | 0.25 | 0.25 |

Frontal area (${\mathrm{m}}^{2}$) | ${A}_{\mathrm{f}}$ | 2.18 | 2.19 | 2.21 | 2.21 |

Rolling friction coefficient ($\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}{10}^{3}$) | ${c}_{\mathrm{r}}$ | 6.5 | 6.5 | 6.5 | 6.5 |

Auxiliary power demand ($\mathrm{W}$) | ${P}_{\text{aux}}$ | 200 | 300 | 400 | 400 |

Wheel radius ($\mathrm{m}$) | ${r}_{\mathrm{w}}$ | 0.293 | 0.316 | 0.326 | 0.326 |

Wheel inertia ($\mathrm{k}\mathrm{g}{\mathrm{m}}^{2}$) | ${\Theta}_{\mathrm{w}}$ | 4 $\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}$ 0.74 | 4 $\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}$ 0.92 | 4 $\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}$ 1.05 | 4 $\phantom{\rule{0.166667em}{0ex}}\xb7\phantom{\rule{0.166667em}{0ex}}$ 1.05 |

Combustion engine displ. volume (L) | ${V}_{\mathrm{d}}$ | 0.8 | 1.2 | 2.0 | 2.0 |

Electric motor power (kW) | 12 | 16 | 20 | N.A. | |

Battery number of cells (-) | 42 | 56 | 70 | N.A. | |

Battery power (kW) | 16.8 | 22.4 | 28 | N.A. | |

Battery capacity (kWh) | 0.62 | 0.83 | 1.04 | N.A. | |

Gearbox nominal torque (Nm) | ${T}_{\mathrm{nom}}$ | 160 | 240 | 400 | 320 |

#### 2.4.8. Engine Scaling

#### 2.4.9. Gear Shifting

#### 2.4.10. Energy Management of Hybrid-Electric Vehicle

## 3. Results and Discussion

#### 3.1. Static Engine Measurements

#### 3.1.1. Consumption Measurements

#### 3.1.2. Nitrogen Oxide Emissions

**Figure 6.**Measured nitrogen oxide emissions (engine out). Measurements for the lean operating region on the left-hand side. Measurements for the stoichiometric operating region on the right-hand side. Emissions are given as a function of engine load; each line indicates one engine speed.

#### 3.1.3. Soot

**Figure 7.**Measured soot emissions (engine out), as a function of engine load, with each line indicating one engine speed.

#### 3.2. Vehicle Emulation Results

#### 3.2.1. Detailed Results

**Figure 8.**Measured vehicle emulation results for the Full-size car with hybrid-electric powertrain on the NEDC.

**Figure 9.**Measured vehicle emulation results for the Full-size car with hybrid-electric powertrain on the WLTP.

**Figure 10.**Measured vehicle emulation results for the Full-size vehicle with conventional powertrain on the NEDC.

**Figure 11.**Measured vehicle emulation results for the Full-size vehicle with conventional powertrain on the WLTP.

#### 3.2.2. Consumption Results

**Table 6.**Summary of the vehicle emulation experiments for all vehicles and driving cycles. Each measurement is repeated three times. The table shows the mean value together with the maximum/minimum deviation of all measurements from the mean value.

Vehicle | Cycle | ${CO}_{2}$ (g/km) | ${\eta}_{\text{ICE}}$ (%) | ${C}_{\mathrm{G}}$ (kg/100 km) | ${C}_{\mathrm{D}}$ (l/100 km) | ${r}_{G}$ (%) | $\mathsf{\Delta}SOC$ (%) | |
---|---|---|---|---|---|---|---|---|

Hybrid | Full-size | NEDC | 68.8${\phantom{\rule{4pt}{0ex}}}_{-0.2}^{+0.5}$ | 35.4${\phantom{\rule{4pt}{0ex}}}_{-0.2}^{+0.1}$ | 2.27${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.01}$ | 0.25${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.02}$ | 92.7${\phantom{\rule{4pt}{0ex}}}_{-0.4}^{+0.3}$ | +0.21${\phantom{\rule{4pt}{0ex}}}_{-0.06}^{+0.05}$ |

WLTP | 77.7${\phantom{\rule{4pt}{0ex}}}_{-0.3}^{+0.3}$ | 34.9${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.2}$ | 2.46${\phantom{\rule{4pt}{0ex}}}_{-0.02}^{+0.01}$ | 0.40${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.01}$ | 89.6${\phantom{\rule{4pt}{0ex}}}_{-0.3}^{+0.2}$ | +1.82${\phantom{\rule{4pt}{0ex}}}_{-0.16}^{+0.17}$ | ||

Compact | NEDC | 55.9${\phantom{\rule{4pt}{0ex}}}_{-0.3}^{+0.4}$ | 35.9${\phantom{\rule{4pt}{0ex}}}_{-0.2}^{+0.2}$ | 1.88${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.01}$ | 0.17${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.00}$ | 94.0${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.2}$ | +0.86${\phantom{\rule{4pt}{0ex}}}_{-0.07}^{+0.04}$ | |

WLTP | 63.9${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.1}$ | 35.9${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.0}$ | 2.12${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.00}$ | 0.22${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.00}$ | 93.2${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | +2.37${\phantom{\rule{4pt}{0ex}}}_{-0.19}^{+0.20}$ | ||

Subcompact | NEDC | 43.0${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.1}$ | 35.9${\phantom{\rule{4pt}{0ex}}}_{-0.1}^{+0.1}$ | 1.40${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.00}$ | 0.18${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.01}$ | 91.5${\phantom{\rule{4pt}{0ex}}}_{-0.4}^{+0.2}$ | +1.37${\phantom{\rule{4pt}{0ex}}}_{-0.03}^{+0.06}$ | |

WLTP | 49.5${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | 36.4${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | 1.67${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.00}$ | 0.14${\phantom{\rule{4pt}{0ex}}}_{-0.00}^{+0.00}$ | 93.1${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | +2.50${\phantom{\rule{4pt}{0ex}}}_{-0.14}^{+0.26}$ | ||

Conv. | Full-size | NEDC | 115.4${\phantom{\rule{4pt}{0ex}}}_{-1.2}^{+0.8}$ | 25.4${\phantom{\rule{4pt}{0ex}}}_{-0.2}^{+0.2}$ | 2.66${\phantom{\rule{4pt}{0ex}}}_{-0.04}^{+0.04}$ | 1.62${\phantom{\rule{4pt}{0ex}}}_{-0.04}^{+0.07}$ | 69.6${\phantom{\rule{4pt}{0ex}}}_{-1.2}^{+0.7}$ | N.A. |

WLTP | 109.1${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | 29.3${\phantom{\rule{4pt}{0ex}}}_{-0.0}^{+0.0}$ | 2.88${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.01}$ | 1.14${\phantom{\rule{4pt}{0ex}}}_{-0.01}^{+0.01}$ | 77.8${\phantom{\rule{4pt}{0ex}}}_{-0.2}^{+0.2}$ | N.A. |

Vehicle | Cycle | Fuel energy (J/m) | Emissions of ${CO}_{2}$ (g/km) | |||||
---|---|---|---|---|---|---|---|---|

Diesel | Gas-Diesel | Change (%) | Diesel | Gas-Diesel | Change (%) | |||

Hybrid | Full-size | NEDC | 1131 | 1226 | +8.4 | 82.9 | 68.8 | −17.0 |

WLTP | 1219 | 1371 | +12.5 | 89.4 | 77.7 | −13.1 | ||

Compact | NEDC | 924 | 1000 | +8.2 | 67.7 | 55.9 | −18.4 | |

WLTP | 1026 | 1140 | +11.1 | 75.3 | 63.9 | −15.1 | ||

Subcompact | NEDC | 708 | 764 | +7.9 | 51.9 | 43.0 | −18.1 | |

WLTP | 807 | 886 | +9.8 | 59.1 | 49.5 | −16.2 | ||

Conv. | Full-size | NEDC | 1614 | 1911 | +18.4 | 118.3 | 115.4 | −2.4 |

WLTP | 1635 | 1853 | +13.3 | 119.9 | 109.1 | −9.0 |

## 4. Conclusions

## Acknowledgments

## Conflict of Interest

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## Share and Cite

**MDPI and ACS Style**

Ott, T.; Onder, C.; Guzzella, L.
Hybrid-Electric Vehicle with Natural Gas-Diesel Engine. *Energies* **2013**, *6*, 3571-3592.
https://doi.org/10.3390/en6073571

**AMA Style**

Ott T, Onder C, Guzzella L.
Hybrid-Electric Vehicle with Natural Gas-Diesel Engine. *Energies*. 2013; 6(7):3571-3592.
https://doi.org/10.3390/en6073571

**Chicago/Turabian Style**

Ott, Tobias, Christopher Onder, and Lino Guzzella.
2013. "Hybrid-Electric Vehicle with Natural Gas-Diesel Engine" *Energies* 6, no. 7: 3571-3592.
https://doi.org/10.3390/en6073571