Abstract
In a world with constantly escalating fuel prices, technologies that not only enhance the efficiency of engines used in automobiles and other equipment, but also are economically viable and environmentally sustainable are the need of the hour.
What if we no longer had to wait for the engine to get warmed up in the miserable winters before we could start it? The hybrid lubrication system is the perfect solution to it and on top of that, it can be used with the existing engine systems without many modifications. The design consists of two smaller, more efficient oil pumps, one electrically powered by a small 5 kW motor and the other, mounted traditionally on the crankshaft of the engine. Unlike traditional lubrication systems where the supply is directly proportional to the engine speed, the proposed design allows for precise control over the flow of the lubricant and the operating pressure of the pumps. By limiting the pressure and flow rate, there is a 4.2% saving in the engine power that in itself contributes to improving the fuel efficiency of the engine and also the reduction in the CO2 emissions. Its operation is similar to that of a hybrid vehicle. The control device regulates the operation of the electric oil pump and depending upon the requirement, automatically activates and deactivates it. At starting conditions, particularly at cold start, to prevent losses from excessive fluid flow and pressure increments, both the pumps work in tandem to supply the lubricant at regulated pressure, thereby achieving the ideal lubrication.
Contrary to the requirement, being mounted on the crank and directly run by the engine, a traditional lubrication system supplies more lubricant at higher speeds and less at lower ones. This is where most of the engine wear takes place and efficiency is compromised. The design solves this problem as it provides the extra lubrication needed at the lower speeds and automatically shuts off the electrical pump and regulates the mechanical pump’s supply to maintain ideal lubrication.
The most important achievement is that both pre and post-operation lubrication of the engine. This allows for a coat of the lubricant to be supplied to the engine components before the initial cranking, prevent metal-to-metal contact and wear. A variable speed motor is used to regulate the operation of the electric oil pump. Depending upon instantaneous requirement, the pump can be brought to work almost immediately. This prevents excessive loading on the engine if it were to operate only under a traditional mechanical oil pump.
The operating pressures are limited to 5-6 bars as compared with the 10-12 bars in a purely mechanical system while the operating flow rates are maintained within the ideal 35 to 40 lpm as compared with the 90 to 100 without the hybrid lubrication system.
Flow measurement and pressure monitor sensors are used to give a closed-loop feedback to the ECU that controls the operation of the electric oil pump and prevents building up of the excessive speed of the mechanical oil pump at higher speeds by relieving the pressure by a bypass-pressure relief valve.