An automotive gas turbine is a type of engine that utilizes a gas turbine to generate power for propelling a vehicle. Unlike traditional internal combustion engines, which rely on pistons and cylinders, gas turbines operate on the principle of converting fuel into high-speed rotating blades. In this article, I will discuss the details of th Automotive Gas Turbine.
Automotive Gas Turbine
A gas turbine essentially consists of two sections — a gasifier section and a power section. The fuel used in a gas turbine can be gasoline, kerosene, or oil. The gasifier section burns fuel in a burner and delivers the resulting gas to the power section, where it spins the power turbine. The power turbine then turns the vehicle wheels through a series of gears.
The gasifier consists of a compressor that has a rotor with a series of blades around its outer edge. As the rotor rotates, the air between the blades is carried around and thrown out by centrifugal force into the burner. Thus, air pressure rises in the burner. The fuel is injected into the burner where it burns and further rises the pressure.
The high-pressure and high-temperature gas then passes through the gasifier nozzle diaphragm. A series of stationary blades directs this gas against a series of curved blades on the outer edge of the gasifier turbine rotor causing it to rotate at a high speed. This gasifier turbine rotor and the compressor rotor are mounted on the same shaft, thus the compressor rotor also rotates at high speed. The action continues to supply the burner with a sufficient amount of compressed air. The action continues as long as fuel is supplied to the burner.
After leaving the gasifier section, the high-pressure, high-temperature gas enters the power turbine. Here, it strikes another series of stationary curved blades which directs it against a series of curved blades on the outer edge of the power turbine rotor causing it to rotate at high speed, about 50,000 r.p.m. This high speed is reduced by a series of transmission gears before the power is supplied to the vehicle wheels.
Major Components of Automotive Gas Turbine
The major components of automotive gas turbines are-
- Combustion Chamber.
- Fuel and start-up Controls.
Either the positive displacement of rotary compressors is used for automotive gas turbines. Out of rotary compressors, the axial flow compressor is not preferred due to its low-pressure ratio (1.2: l ). A multistage compressor would be needed to achieve the pressure ratio of 4:1 designed for automobile applications. A centrifugal compressor also achieves this pressure ratio.
The turbines used for automotive applications may be axial flow and radial flow types because they have good air handling characteristics. A radial flow turbine has an efficiency higher than that of an axial flow turbine over a wide operating range. The radial flow turbines are much more speed-sensitive than the axial flow turbines.
Regenerators are used in automotive gas turbines for heat exchange. A rotary-type periodic flow regenerator is commonly used. In a disc regenerator, the compressor air flows axially through a sector of a slowly rotating disc, the hot gases flowing in the opposite direction through the rest of the disc. In the drum regenerator, the compressor air flows radially inward through the matrix, and the hot gases radially outward through the matrix on the other side of a bulkhead through which the drum slowly rotates.
#4. Combustion Chamber
Can type combustion chamber is most commonly used. It consists of an inner chamber that admits the primary air through swirl vanes near the fuel jets of the injector nozzle. The combustion chamber can be divided into three zones -primary, intermediate, and secondary. The main combustion occurs in the primary zone. In the intermediate zone, the combustion reactions continue to release energy. In the secondary zone, an extra quantity of air is supplied to lower the temperature of combustion products so that the turbine inlet temperature is within the permitted zone.
A transmission system is used to get the speed reduction because the turbine speed is much faster than the conventional automotive engines. Different transmission designs are considered for the gas turbine engines :
- Continuously variable transmission.
- Multispeed gearbox with controlled slip clutch.
- Variable ratio belt drive.
- Hydromechanical drive.
- Hydraulic torque converter.
#6. Fuel and Start-up Controls
The Brayton engine combustion chamber is a constant pressure continuous type combustion chamber and it can burn a wide variety of fuels. Typical automotive gas turbine fuels may be gasoline and diesel, without any octane or cetane requirements, methanol gasoline, methanol, and kerosene. The present-day automotive gas turbine is capable of giving good specific fuel consumption compared to the conventional engine.
Chrysler Corporation developed a turbine-powered vehicle. It consists of a single-stage centrifugal compressor with a pressure ratio of 4:1:1 a compressor airflow of 1 kg/sec and a single-can type combustion chamber. There are six generation gas turbines.
The first and second stage turbines are of axial type and the second stage turbine has variable geometry stator. Two rotating disc-type regenerator runs at 22 rpm. The regeneration effectiveness is 87%. The efficiency of the compressor, first stage, and second stage turbine are 77%, 88%, and 7 I % respectively. The maximum turbine speed is about 45700 rpm while the maximum output speed is 4700 rpm. The rated power of the engine is 150 BP at 5000 rpm output shaft speed.
Uses of Automotive Gas Turbines
There are a lot of fields where the automotive gas turbines are used. These fields are-
A small gas turbine is used for supercharging. It is run by exhaust gases and drives the supercharger for gasoline engines and heavy-duty diesel engines.
2. Turbojet and Turbo propeller Engine
The turbine supplies power only to drive the air compressor in the turbojet engine; and in turbopropeller engines, it may drive the propeller and the compressor also.
3. Marine Field
The gas turbines can also be used in the marine field. Unlike in a power plant using a steam turbine, no boiler, water storage tanks, and distillation plant are required. The high thermal ratios to be used for this purpose require a large heat exchange.
The gas turbines are also used in locomotives. The Brown Boveri of Switzerland built the first gas turbine locomotive in 1941. The power developed by the engine is 7900 IP out of which 5725 IP is consumed to drive 18 stage axial flow compressor. The generator delivers de four electric motors mounted on each driving axial. It runs at speeds up to 110 km/h.
The General Electric Co. U.S.A. in association with American Locomotive Co. has successfully built some 4870 IP locomotives running on the gas turbo-electric principle. Many other manufacturers in the world are concentrating on manufacturing locomotives powered by gas turbo-electric units.
5. Road transport
Small gas turbine cars have been successfully manufactured and tested for road transport. Heavy-duty vehicles powered by gas turbines are also being manufactured.
6. Electric Power Generation
Gas turbines are widely used now for electric power generation. As compared to steam power stations, the gas turbine power station can be installed and maintained at less cost. It can also be started and brought up to full load quickly.
Gas turbines are also used for many industrial processes like blasting of air for blast furnaces in steel industries, oil, and other chemical industries.
Advantages of Automotive Gas Turbine
There are certain advantages available in the automotive gas turbine. These advantages are-
- The gas turbine is smooth in operation and continuous in performance.
- It does not have any reciprocating part, hence it is easy to balance. It is free from vibrations.
- There is no sequence of suction, compression, ignition, and expansion, as in the petrol engine.
- Once the spray has been ignited by an electric spark, combustion is continuous and no further ignition is necessary.
- A flywheel is not required because the turbine exerts a smooth and continuous torque on the shaft.
- It has higher mechanical efficiency.
- It is compact in shape, simple in design, and light in weight.
- Although the initial cost is high, the maintenance cost is low.
- It can use cheaper fuels.
- Oil consumption is low.
- It has low internal friction and resistance.
- There is no need for clutches and a gearbox in it except for reversing.
Disadvantages of Automotive Gas Turbine
If there are advantages then there are the disadvantages also. The disadvantages of the automotive gas turbines are-
- The gas turbine, in its simplest form, consumes 70% more fuel than a petrol engine for the same power.
- Due to the very high speed, the gas turbine causes serious problems in obtaining an effective transmission speed suitable for road speeds.
- Breaking is also not affecting due to very high speed. The average turbine speed varies from 25,000 to 50,000 r.p.m.
- A high-speed self-starter motor and a large battery are required.
- A serious objection to the use of gas turbines on road vehicles is a large number of exhaust fumes, a nuisance, and hazards on the road in heavy traffic.
In summary, while gas turbines have demonstrated their capabilities in certain applications, their use in automotive settings has faced challenges that have limited their widespread adoption in production vehicles. Advances in technology and ongoing research may, however, influence the prospects of gas turbines in the automotive industry.
Frequently Asked Questions(FAQ’S)
What is an automotive gas turbine?
An automotive gas turbine is an engine that utilizes a gas turbine to generate power for propelling a vehicle. It operates on the principle of converting fuel into high-speed rotating blades to drive the vehicle’s wheels.
Have gas turbines been used in production vehicles?
While there have been experimental and prototype gas turbine-powered cars, widespread commercial adoption has been limited. The Chrysler Turbine Car in the 1960s is a notable example.
Can gas turbines be used in hybrid or electric vehicles?
While traditional gas turbines may face challenges in hybrid or electric vehicles, there is ongoing research into using microturbines or turbine-based range extenders in hybrid systems to address specific efficiency issues.