Steam Engine Efficiency

Prospects for Gas/Air Turbine Powered Thermal Rechargeable Ship Propulsion

By Harry Valentine

The history of ship propulsion began with the development of steam piston engines that were displaced by steam turbines engines on the largest commercial ships. Over time the steam engines gave way to diesel engines and occasionally gas turbine turbines that provide commercial maritime propulsive power. While navy services may favor gas turbine engines due to high output from compact dimensions, such engines typically operate at optimal efficiency while delivering peak output. They generally operate at lower thermal efficiency than do diesel engines and especially so while operating at reduced output.

New developments in the power industry has created potential for a thermally efficient, externally heated gas/air turbine engine to be adapted for commercial marine propulsion. The nuclear power industry is developing high-temperature technology of up to 1000C (1832F) that can activate high-powered, closed-cycle, externally heated turbine engines that flow either helium or carbon dioxide gas at extreme pressure. The low pressure upstream of the low-pressure compressor may be 7-bar to 10-bar (100-psi to 150-psi) and peak system pressure may reach 45-bar to 65-bar (650-psi to 950-psi) immediately upstream of the high-pressure power turbine.

Possible Marine Turbine:

Using highly pressurized gas within the turbine system gas allows an extremely compact engine to deliver very high power output. The ability to vary the pressure in the turbine system allows for variable engine output dropping to as low as 25% of maximum output, at very high efficiency. The outer dimensions of a closed-cycle, externally heated air/gas turbine engine of 20Mw to 50Mw output and capable of propelling a ship may theoretically fit inside the box of a delivery van. For marine service, the engine may operate using highly pressurized atmospheric air.

Operating on the ocean allows for water-cooling of certain engine operations, such as the intercooler that cools the air between the low-pressure and high-pressure turbo compressors. There may be additional need to cool the pressurized air within the turbine system immediately upstream of the low-pressure compressor. A recuperative air-to-air heat exchanger would transfer exhaust heat leaving the low-pressure power turbine to preheat compressed air flowing from the high-pressure compressor. That compressed air would be further heated to a much higher temperature in a high performance heat exchanger that sources heat from a thermal storage system.

Summer, vacations and observatories « Astrophotography

I thought I’d write something regarding my summer activities. Amateur astronomy is very quiet during the summer season due to the light skye for the most part, the quick changing weather circumstances from day to day, but also because for a common Swede the summer season is dedicated for the anual vacations from work and studies. My family and I decided to visit Scotland this year, which was very beautiful. We decided to visit the major cities such as Glasgow and Edinburg, but also the country side of Scotland, such as lakes (Loch Lomond, Loch Drunkie) and parts of the Scotish Highlands. Scotland got rich scientific and engineering history. One interesting story is that of Scotsman James Watt (known from the unit Watt written on every light bulb you buy at stores). Watt was a poor engineer fighting with his economy issues most part of his life. He owned a little store selling his navigational instruments in Glasgow, but barely made any money that suffice for his family living at the time. Years passed and James suceeded getting an employment at the university of Glasgow, enabling him to access the university workshop.

Just as other innovators, James did what most people did not. He had passion in details and improvement. He analyzed the classical steam engine and found some basic flaws and weaknesses in the current system. At the time steam engines were very small and used for the most part in the Scotish country side, helping miners to pump out water from the coil mines.

James found out that Newcomen’s model of steam engine had very low efficiency. After some long nights and big efforts James finally found a way to improve the steam engine and win a high degree of efficiency at low cost. To make a long story short, his solution revolutionized and changed the world. His ingenious methods and solution to the steam engine was a major turning point in history changing the way of living. It is what we call today as the industrial revolution.

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