For Yulin Public Transport Corporation, September 3 is a date that should be remembered for ever. On this day, 30 new-energy conditioned public buses were put into application formally, which signified the new breakthrough of Yulin Public Transport in the aspect of new energy utilization, energy conservation and environmental protection.

As of today, the new-energy public buses have run along the two routes of Route No.3 and No.7 for over two months. What on earth will the performance of the new-energy public buses of this batch be? We interviewed, in the bus, the driver of Yulin Public Transport and the engineers of the New-Energy Power R&D Institute of Yuchai R&D Center. So, let them unveil the mysterious mask of new-energy public buses.

It is learned, all of the said 30 new-energy public buses applied to Yulin Public Transport Corporation are equipped with Yuchai engine and Yuchai hybrid power assembly system. They adopt natural gas as the fuel, using gas and electricity at the same time. The emission meets with National Standard V. This hybrid power assembly system adopts the single shaft parallel structure that is the mainstream in the world. With the engine and low-speed high-torque PMS motor arranged in the same shaft, the system is characterized with such advantages as compact structure, high mechanical efficiency and good reliability. Besides, thanks to Yuchais optimization in such aspects as engineering, technical details, quality and strategy, the hybrid power assembly system of Yulin Public Transport draw plentiful of attention for such advantages as being economic, comfortable and reliable.

Being economic: compared with traditional public buses, over 30% of the energy can be saved

As the economy develops, energy restriction becomes tight. As the major subject of energy consumption, energy conservation technology becomes the magic weapon to dominate the market of automobile industry. Yuchai hybrid power system wins the preference of automobile enterprises and end users for its excellent energy conservation effect.

At present, Yuchai hybrid power system has already been applied to the passenger buses of several major brands such as Guangzhou Automobile Group Autobus Co., Ltd., King Long Motor Group, Zhongtong Bus, Youngman Bus, etc., shuttling in such cities as Guangzhou, Wuhan, Yuhang, Guiyang, Kunming, etc.

It is reported, compared with traditional public buses, Yuchai hybrid power system can save over 30% of the energy.

An engineer of New-Energy Power R& D Institute of Yuchai R&D, Chen Hongquan is retrieving the data concerning public buses

During the driving of the public buses, the complete-vehicle control strategy of Yuchai hybrid power system can guarantee that the engine of the buses can be operated under the most economic and efficient working condition. Besides, when the public bus is caught in a traffic jam or waiting for the signal light to change from red to green, the function of automatic start and stop of this system can avoid energy waste due to low-speed operation of the engine, an engineer of New-Energy Power R& D Institute of Yuchai R&D, Chen Hongquan said.

Regenerative braking function is another distinctive characteristic of Yuchai hybrid power system in terms of energy conservation. In the braking of traditional vehicles, the brake pad will consume the kinetic energy of the vehicles, so as to realize braking. This process is actually a waste of energy. For the new-energy vehicles equipped with Yuchai hybrid power system, when the driver depresses the braking pedal, the motor will generate power and produce automatic resistance. Meanwhile, it recovers the kinetic energy that may be wasted into the battery for starting the vehicle.

Li Zhengtu is an older driver that has been driving for ten years. Now, she works in No.2 Vehicle Team of Yulin Public Transport Corporation, taking charge of the scheduling of public buses. She said, the vehicle body of the new-energy public buses of this batch is bigger than that of the former public buses in the vehicle team, they can carry more passengers and they are equipped with air conditioners. But, their operating cost is lower than the original public buses.

It is learned that synchronously driven by engine and motor, Yuchai hybrid power system is able to satisfy the dynamic requirements of the buses. In the meanwhile of being advantageously economic, its kinetic power is not affected at all.

The Director of Hybrid Power Assembly Development Office, New-Energy Power R&D Institute of Yuchai R&D Center, Mao Zhengsong introduced, the new-energy vehicles equipped with Yuchai hybrid power system adopt the economic mode with the starting gear being Gear 3; when big dynamic power is required, it will be shifted into the dynamic mode (the rotating speed of the engine will be increased by 200rpm when the gear is shifted) with the starting gear being Gear 2;  while driving on the ramp, the starting gear will be Gear 1.

Driver Liang said, the throttle of the new-energy public bus equipped with Yuchai hybrid power system is very accurate. It can supply the oil accurately as you require. Thus, it can fully satisfy the dynamic requirement of the operation of Yulin Public Transport.

Comfort: All drivers love to drive the new-energy public buses

After getting in the tidy and spacious public bus, Driver Zhong told us, this new-energy public bus is convenient to drive. Moreover, the noise of the engine is low and the vibration is minor. More importantly, the smoothness of the vehicles is essentially improved compared with traditional public buses.

Driver Zhong was driving the new-energy public bus steadily

Yuchai hybrid power system can realize intelligent and automatic gear shift through automatic gearbox. In addition, the clutch pedal of traditional public bus is replaced with automatic control system. Therefore, when the driver is driving the bus, the driver doesnt need to shift the gear with his/her right hand, neither does  he/she need to depress the clutch with his/her left foot. In this way, the right hand and the left foot of the driver are freed, the driving operation is reduced and the intensity for the driver is greatly reduced.

The author got on the bus for a journey, with a view of checking whether the new-energy public buses were like what was described by the driver. And I indeed found they are utterly different from that of traditional public buses. Since this new-energy public bus is provided with air conditioner, the van of this bus is closed and the inside of the bus is quiet. To experience obvious vibration, the author chose to sit in the rear part of the van. When the public bus started, the author didnt experience any obvious vibration of the vehicle body. Instead, it was very comfortable to sit on the bus.

The passengers say they are comfortable when sitting on this bus and I feel comfortable when I drive it, Driver Zhong said with a smile.

Li Zhengtu told the author, at present, only Route No.3 and No.7 among the public transit routes of Yulin are provided with new-energy buses. Since it is comfortable to drive new-energy buses, all the drivers of the vehicle team are willing to drive new-energy public buses.

Reliability: no break-down or towing service within over two months since the operation

At present, the several key factors that may influence the competition of hybrid power system in domestic market include energy conservation effect, reliability and integrated cost. Yuchai hybrid power system wins the unanimous praise among the customers for its outstanding reliability.

The hybrid power system of Yuchai is provided with emergency start function after high-voltage failure. Once the electrical control system fails, the driver can still drive the bus in conventional mode. Thus, the reliability of the system is enhanced. As a matter of fact, this mainly benefits from the unique clutch control mechanism and complete-vehicle control strategy in Yuchai hybrid power system.

Due to the particularity of providing public services, once the public bus breaks down, the travel of the general public will be badly affected. Besides, towing will also bring about much trouble to public traffic. When Yuchai hybrid power system breaks down under the mode of electrical power, the driver can start the emergency mode, pull the bus (purely driven by the engine) over the roadside, or drive the bus to the nearby repair shop directly. Otherwise, when the engine breaks down, the public bus cannot pull the bus (purely driven by electrical power) over the roadside, Chen Hongquan introduced.

The new-energy public buses were applied in Yulin for the first time. To guarantee the normal operation, the New-energy Power R&D Institute of Yuchai R&D Center dispatched the technicians to track the service throughout the process. They not only provided trainings to the drivers of the Public Transport Corporation, they even taught them the driving techniques without any concealment. Thanks to the prudent consideration of Yuchai, the running-in period of new-energy public buses of this batch from application to normal operation was greatly reduced.

Driver Liang told us, the new-energy public bus driven by him has not yet broken down. Occasionally, some minor trouble may occur. But, he can manage it by himself. However, the performance of Yuchai hybrid power system was exceptionally steady. It had never broken down.

Li Zhengtu was making the scheduling.

The 30 new-energy buses have been put into application for over two months. They have not broken down or been towed, Li Zhengtu continued, This also saves a lot of maintenance costs for the Company.

Mao Zhengsong was very confident of the hybrid power system of Yuchai. He said, our system was provided with a gearbox, the application scope of the working condition was broad, the electrical power rate adjustment was rather flexible, and the oil conservation rate was high and stable. The motor power of our system was 100kW, while that of the same industry only reached 65kW. Besides, we were endowed with an inborn advantage in the understanding and control of engines and our service network was also incomparably better than that of our opponents.

In future, new-energy buses will be the mainstream, Yuchai has already made full preparation in this aspect. According to Mao Zhengsong, Yuchai has already formally promoted the plug-in hybrid power system, to satisfy the requirements of the state concerning new energy subsidy during 2013 to 2015. Afterwards, Yuchai will promote more and more sophisticated hybrid power system technologies, so as to seize the market heights.

(Yang Mingze)