Soviet experiments: starting a diesel engine using a gunpowder gas generator
In 1981, the Soviet Armored Vehicles Bulletin, a specialized journal dedicated to various researchers and innovations in the development, improvement, and operation of combat vehicles, published an interesting article on starting a diesel engine using a solid-fuel gas generator.
Although these devices never went into production, the article is quite interesting from a technical perspective, especially since the gas generator was tested on a BMP-1 engine rather than being calculated purely theoretically. So, it's highly recommended reading.
Starting system with solid fuel gas generator for diesel engine
The main drawback of electric and air-starting VGM diesel engines is a significant reduction in efficiency at low ambient temperatures (AT). Current requirements stipulate a pre-start time of no more than 15 minutes at AT = -40°C. At temperatures above -25°C, engine starting must be possible without preheating the coolant, oil, and battery electrolyte.
These requirements can be met by a system using the energy generated by the combustion of a solid propellant propellant charge. The gas generator is a source of thermal, potential (gas pressure), and kinetic energy of the gases. Two design options are possible: one with direct injection of gases into the engine cylinders and one with the use of gas energy in a special starter that rotates the crankshaft. tank engine.
The well-known powder starting system for multi-cylinder diesel engines has starting cartridges mounted on the cylinders, sequentially detonated by mechanically controlled strikers. The strikers are triggered by cam-type firing synchronizers connected to the engine shaft. Gases are supplied to each cylinder only during the first expansion stroke, which is not always sufficient for starting the diesel engine. Another disadvantage of this starting device is its complex design and the labor-intensive nature of reloading.
Research was conducted on a direct-start system (figure), in which hot gases from a single gas generator are fed into the engine cylinders through an air distributor and starting valves. The use of air-starting units for a system with a gas generator significantly simplifies the system design. Gases are fed into the engine cylinders in accordance with their firing order.
To reduce heat buildup and increase the reliability of the gas generator, the housing 4 is constructed using multiple layers. It consists of a load-bearing shell, a heat-insulating coating, and a thin-walled sleeve installed with a gap. The sleeve protects the heat-insulating coating from damage. Fuel element 5 is made of NDP-5A, a composite with a combustion temperature of 1600 K under normal conditions.
Reliable generator starting is ensured by a combined initiating device consisting of a UDP-2 pyrotechnic cartridge, a DRP propellant charge, and a RNDSI-5K propellant pellet. The charge and pellets are glued to the fuel element. The pyrotechnic cartridge 7 is installed in a threaded hole in the gas generator cover. The system is equipped with a safety membrane device, installed in adapter 3 upstream of discharge nozzle 1 and designed for an actuation pressure of 11,8–13,7 MPa. Cover 6 has a locking connection, ensuring rapid generator recharging.
Testing of the experimental starting system with a solid-fuel gas generator was conducted on a UTD-20 6-cylinder, 4-stroke engine. At tо.с. = 15 ÷ 20°C, MT-16P oil was used in the engine lubrication system; at sub-zero temperatures, low-viscosity MTZ-10P oil was used. The gas generator was connected to the diesel air distributor via a 1200 mm long gas duct. An LH-412 sensor was used to measure pressure, and an OR-310 temperature sensor was used to measure temperature.
Crankshaft speed was determined by the time and angle of its rotation, which was measured by an inductive sensor with a 1/114th-revolution marker. System performance during cranking (without fuel injection) of the UTD-20 engine was recorded with an oscilloscope (Table 1).
The obtained starting system parameters confirmed the accuracy of the preliminary calculations for gas flow rate Q and gas generator operating time. At all gas flow rates, the crankshaft speed was sufficient to start the engine under these conditions. When the gas generator was operating at Q = 45–56 g/s, the crankshaft speed increased significantly due to the increased gas temperature, which initiated oil ignition in some cylinders. When the gas generator was operating at flow rates starting at 30 g/s and fuel was supplied to the cylinders, the engine started on the first attempt in no more than 1 second.
To evaluate the gas consumption and gas generator operating time required for reliable engine starting at subzero ambient temperatures, start-up tests of the UTD-20 engine with an experimental starting system were conducted in a BMP-1. Cold starting of this diesel engine without starting aids is ensured down to a temperature of -5°C. Tests were conducted with and without a nozzle-less torch intake air heater (Table 2).
Tests have shown that a reliable start of the UTD-20 engine at tо.с. = -15°С requires a gas flow rate of ~75 g/s with the generator running for ~3 s. To ensure these gas generator parameters, a fuel element weighing ~225 g is required. Moreover, the gas pressure before the air distributor does not exceed the permissible values for the UTD-20 engine (see Tables 1, 2).
Conclusion: The conducted studies have demonstrated the fundamental possibility of creating a solid-fuel launch system that is effective at low ambient temperatures.
Source:
"A Starting System with a Solid-Propellant Gas Generator for a Diesel Engine." S. Yu. Serebrennikov, Yu. A. Sukhoveev, V. N. Sysoev. "Bulletin of Armored Vehicles," No. 6, 1981.
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